Map

The May 18, 1980 eruption of Mount St. Helens involved a complex series of
events that unfolded over 12 hours, with many events going on simultaneously.
These volcanic events buried some areas in debris
avalanches and mudflows,
scoured other areas with hot gases, blew down or scorched forests on slopes
several miles away, and dusted forests farther away with volcanic ash. Entire
forests were toppled by the hot blast. Most plants and animals perished, meadows
were destroyed, and numerous new ponds and lakes were created.

The eruption included many types of physical forces, such as heat, burial,
and scour, and the intensity of these forces varied substantially over the
blast area (for example, thin versus thick deposits, warm versus searing
hot temperatures). Generally, these physical forces were most intense in areas
closest to the volcano’s north side and less severe farther away, but
the mountainous terrain shielded some spots from heat and funneled mudflows
into stream valleys. Also, multiple forces affected many places. So, although
the whole landscape looked gray and ashen, scientists found complicated patterns
of disturbance and tremendous variation, or heterogeneity, in the effects on
the ecosystems. Ultimately, the eruption created a complex mosaic of disturbance
zones.

Browse the thumbnails below to learn more about the disturbance zones created
by the eruption.